The invention relates to a measuring instrument for measuring bioluminescence and chemiluminescence.
Bioluminescence and chemiluminescence have come into widespread use in medical applications for the investigation of a very wide variety of specimens. One reason which has contributed to this is the fact that it is not necessary to work with radioactive materials, whose manipulation and storage is troublesome and expensive for many users.
In bioluminescence and chemiluminescence, a special substance (activator) is added to the specimen to be investigated, and in particular injected thereinto, after the addition of which a relatively rapid reaction ensues which is associated with the emission of light. This light emission can be detected by a suitable optical detector, e.g., a photomultiplier, and converted into an electrical signal, after which it is possible, from the intensity of the light signal and the time lapse, to draw conlusions as to the nature of the specimen and, in particular, the presence of specific substances.
An essential aspect of this method is that, because of the rapidly occurring light reaction, the activator can only be injected if the specimen has already reached the point of measurement in front of the light entry port of the optical detector.
It is obvious that the point of measurement, i.e. the area in front of the light-sensitive opening of the optical detector, must be completely shielded from stray light, at least during the measuring procedure in order to achieve reliable results of measurement. The complete sealing of the point of measurement requires a certain technical complexity in customary commercial instruments as exemplfied in applicant's Published German patent application No. 3,239,866, which relates to a dimmable measuring station for a photometer.
Another requirement imposed on such measuring instruments lies in the fact that they must be able to measure the largest number of specimens as efficiently, i.e. as automatically, as possible, that is to say, that the specimen pan with the substance to be measured is brought to the point of measurement, the activator(s) is/are injected thereinto, and the specimen pan remains at the point of measurement until the light reaction has decayed.
In the above-cited Published German patent application No. 3,239,866 and in applicant's commercially available instrument ("Autobiolumat LB 950"), an attempt is made at the same time to satisfy these requirements by introducing a large number of specimen pans in holders which can be coupled together and by moving them past the point of measurement therebeneath. Here, the point of measurement incorporates a housing block with a cylindrical interior, which is connected to the light entry port of the optical detector. The holders for the specimen pans are open at the bottom so that, by means of a piston mechanism, one specimen pan at a time can be pushed from below into the housing block, and thus to the point of measurement.
Thus, for the measuring process, each specimen pan is pushed out of its own holder by a vertical lift and is returned thereto after the measurement has been completed, after which the chain of holders coupled together is moved further by one link and this measuring process is repeated.
Admittedly, this prior art approach produces a certain automation effect owing to the fact that the holders for the specimen pans are coupled in chain-like fashion but, on the one hand, the means for lifting the specimen pans vertically to the point of measurement and, on the other, the means for light-tight shielding of the point of measurement when a specimen pan is introduced thereinto call for a high mechanical precision, and they are therefore relatively expensive. The time required for the lifting motions must be added to the time of the actual measurement, and thus constitutes dead time, which deleteriously affects the efficiency of measurement of many specimens.